International Pig Topics — Volume 30 Number 5 7

by Johannes Kauffold, Large AnimalClinic for Theriogenology andAmbulatory Services, Faculty ofVeterinary Medicine, University ofLeipzig and Miquel Collel, Director,Scientific Marketing Affairs, GlobalSwine, Merck Animal Health.

In Europe, and increasingly also in NorthAmerica, ultrasonography – for which theterm ‘scanning’ is commonly used – has

been implemented on swine productionunits. This technique can be ideallyperformed through the skin, usually of theabdomen (which is then called‘transabdominal’ or ‘transcutaneous’),without the need to penetrate the animal viathe rectum, as is commonly the case inhorses or cattle. The main purpose for scanning pigs is to

test for pregnancy. Indeed, scanning issuperior to other methods of pregnancydiagnosis. The main advantage is that, evenwith relatively simple scan units, it allows for

early use (starting day 20/21 after breeding;Fig. 2A), combined with its accuracy at eventhis early stage of pregnancy (close to100%). Besides ‘normal’ pregnancy, failures of

pregnancy can also be diagnosed. Forexample, dead embryos or foetuses can bediagnosed on the basis of missing heartbeats or missing blood flow throughumbilical blood vessels (the latter can onlybe determined by using Dopplerultrasonography; Fig. 2B). Also, situations of embryonic mortality or

abortions have been well described byultrasonography and can be unambiguouslydiagnosed. Previously, the main disadvantage of using

ultrasonography on farms was the relativelyhigh price of the machines together with ahigh weight which limited portability andmade scanning, especially of loose-housedpigs, almost impossible.Over recent years, prices have dropped

dramatically while ‘quality factors’ such as

resolution and portability improved, and‘good’ machines are currently available for areasonable cost. One among ‘good’ machines is the HS

1600 (Fig. 1 with inserted picture) which is ahand-held unit with a smooth and thus easyto disinfect surface. Another advantage isthe absence of a ventilation fan whichprevents potential spread of porcinepathogens into the surroundingenvironment. However, scanning offers more than

merely testing for pregnancy. Withultrasonography, both the non-pregnantuterus and the ovaries can be visualised.Imagine the many situations when youwanted to have a look inside the animal butfailed for obvious reasons. Using ultrasound,gilts and sows are now virtually transparent!Besides pregnancy testing, this unique formof ultrasound can be used for multiplepurposes in breeding pig facilities. Thosepurposes are:

l Checking ovulation The ovary and all the ovarian structures thatappear around ovulation are well described.Even after completion of ovulation, when allpre-ovulatory follicles (Fig. 2C) have beenovulated, the ovary can be clearly identifiedon the basis of the presence of corporahaemorrhagica (Fig. 2D). This allows for checking when ovulation

occurs in individuals and in groups ofbreeding sows. Scanning to check forovulation is useful whenever there arequestions relating to the breedingmanagement and timing of insemination inparticular.‘Checking for ovulation’ is also a central

element in diagnostic troubleshootingprocesses of many cases of failure inreproduction.

l Checking puberty statusAs the pig matures sexually and changesfrom the pre-pubertal to the pubertal stage,there is uterine growth and the giltscommence their cycling activity, with thefirst ovulation and subsequent developmentof corpora lutea or ‘yellow bodies’ in theovary. Scanning allows for the visualisation of the

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How ultrasound hasrevolutionised reproductionmanagement

Fig. 1. Procedure of transabdominal ultrasonography of pigs. A transducer (sector,convex or micro-convex preferred, but linear principally possible too) is placed hori-zontally just above the last pair of teats onto the ventral right abdomen. Insertedpicture: A HS 1600 (Honda Electronics Ltd, Tokyo, Japan) is a ‘good’ choice for anultrasound machine to be used on pig farms due, at least in part, to its portability,easy-to-handle settings, a surface that can be disinfected, a good resolution and areasonable price.

8 International Pig Topics — Volume 30 Number 5

uterus and the ovaries in both the pre-pubertal and the pubertal gilt and theassessment of both organs can give valuableinformation on sexual maturity. If the ovary is scanned, animals having only

small follicles are considered pre-pubertal,while those having large, pre-ovulatoryfollicles or ovarian structures indicatingcompleted ovulation (corpora lutea) arepubertal. Scanning the ovary as an ‘indicator’for puberty status has proven to give 100%accuracy.If the uterus is used for assessment, the

uterine size has proven to be almost reliableas the ovary in the assessment of puberty. Inorder to make this assessment, the uterushas to be imaged as a cross-section, thenmeasured in two dimensions and the cross-sectional area calculated. Pre-pubertal giltshave a cross-sectional area of ≤1cm2, whileit is ≥1.2cm2 in pubertal animals (thistranslate to diameters of roughly ≤0.9 and≥1.1cm, respectively). Maximum accuracy in the assessment of

puberty status is, however, achieved if boththe uterus and the ovaries are scanned.

l Examination of females with reduced orcomplete cessation of fertilityIf a female displays reduced fertility orabsence of fertility, this can be for differentreasons. Scanning is directly helpful if thereason is the female herself, with defectsrelated to the ovaries and/or the uterus. The oviduct is yet not assessable in the pig.

Ovarian cysts are usually considered onemain reason for the animals’ failure tobreed. However, it is only polycystic ovarian

degeneration (POD), where the ovary hasonly cystic ovarian structures, which is fatalto fertility, while single or multiple cystsaccompanied by ‘normal’ ovarian structuresare more frequent but of lesser significance.

Cysts (in terms of number and ‘quality’)can indeed be identified usingultrasonography (Figs. 3A and 3B) andfemales with POD quickly culled, therebyreducing the number of non-productivedays. Amongst females exhibiting fertility

problems, many have uterine infections such

as inflammation of the endometrium orlining of the uterus. Although the chronicinflammation is more prevalent, the acutetype can sometimes be observed combinedwith a purulent vaginal discharge.Unfortunately, scanning allows only for thedetection of acute endometritis, andrecognition usually occurs on the basis ofabnormal flocculent or clotted fluid withinthe uterus. The echotexture is another parameter

used to describe the appearance of theuterus in ultrasound images and uses thedistribution and frequency of lighter anddarker areas for description. The echotexture can be described as

homogeneous (Fig. 4A) or heterogeneous(Fig. 4B) and undergoes normalphysiological changes during the oestruscycle. It is heterogeneous when femalesapproach or are in heat and larger folliclesare present, and homogeneous at any otherstages of the oestrus cycle, for examplewhen corpora lutea are present. Any deviation from the physiologically

normal status might be consideredabnormal and is associated with reducedfertility. A third parameter, uterine size,might also be helpful in assessment ofwhether a uterus is functioning normally ornot.The size is determined as described for

gilts and is given as the sectional area.Uterine size has been shown to correlate

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Fig. 2A. Image obtained from a gravid pig showing an example of uterine cross-sec-tions containing embryonic fluid and the embryo itself (white arrow) on day 23 afterbreeding. Fig. 2B. Cross-section of a gravid uterus with a foetus (white arrow) on day66 of pregnancy. Coloured signals are from blood flow within blood vessels of theumbilical cord demonstrating viability of the respective foetus (red arrow). Fig. 2C.An ovary with several large (approximately 6mm) follicles (white arrows) ‘ready’ forovulation. Fig. 2D. An image from an animal immediately after ovulation. One cross-section of the uterus is marked (white arrow). Next to it is an ovary bearing severalcorpora haemmorhagica (little white arrows) located within the area circled with adotted line.

2A 2B

2C 2D

International Pig Topics — Volume 30 Number 5 9

with uterine weight and the weight itselfhelpful in the diagnosis of uterine disorders.For instance, the mould toxin zearalenone,

which can cause reproductive problems inpigs, has been associated with very small(light) and very heavy reproductive tracts.Finally, uterine perfusion (i.e. blood supply)has been advocated as another usefulparameter in combination with i.e.echotexture in the assessment of uterinefunctionality and health, and studies arecurrently ongoing to test this usefulness.

l Practical use of ultrasonographyWith its multipurpose usage potential,ultrasonography can be much more thanmerely a procedure to test for pregnancy.Given that pregnancy diagnosis may beperformed on day 20 or 21 after breeding,non-pregnant females can be detected rightat the time they are presumed to return toservice, so they can be subjected to veryclose heat detection supervision. The concurrent assessment of the ovaries

and the uterus in these non-pregnantfemales gives additional benefit. Asmentioned before, animals with POD canbe culled immediately. However, as a number of non-pregnant

animals will have corpora lutea or smallfollicles, producers might be willing to treatthem hormonally to induce oestrus and/orovulation.Finally, animals with obvious uterine

alterations, such as abnormal intrauterinefluid or atypical echotexture and thusreduced fertility, can be quickly sent toslaughter. This entire procedure, in combination with

routine pregnancy testing, including ovarianas well as uterine diagnosis, will certainlyincrease productivity through the reductionof non-productive days.Besides individual pig scanning, and thus

more importantly, is the use ofultrasonography strategically in cases ofreproduction trouble-shooting. The list of‘troubles’ where ultrasonography can be‘valuable’ is long and includes:l Low conception rate.

l Low farrowing rate.l Low litter size.l Long wean-oestrus-interval.l High number of sows with no-heat afterweaning.l High number of returns.l Late fall-outs.l Abortion.l High number of gilts with delayed or noattainment of puberty.l Discharge syndrome in both sows andgilt.In addition, using ultrasonography it is

possible to assess the urinary bladder, anorgan that is very often ‘affected’ (such asdue to sediment which, if presentmoderately or heavily, is associated with anincreased incidence of urinary tractinfection). Also, first attempts have beenmade to test if ultrasonography can providevalue to the assessment of functionality andhealth of the mammary gland, and resultsare looking promising. Any of the aforementioned problems

would require a separate ‘problem-adapted’approach of diagnosis. However, there are‘common’ elements’ that many problems

share; for instance, in case of lowconception and farrowing rates, but alsolow litter size. In all these cases it would make absolute

sense to start the diagnostic procedure withchecking ovulation times in an examplepopulation, to make sure that inseminationtimes were accurate. Another good example for using

ultrasonography in ‘first place’ is long wean-oestrus-interval or no heat after weaning. For example, sows may suffer from

anoestrus after weaning due to high ambienttemperature in summer or as part of‘second litter syndrome’ as the result ofmetabolic insufficiency, and then will haveinactive ovaries as can be clearly seen byultrasonography. In contrast, in several cases where no heat

after weaning has been reported, heatchecking procedures were finally identifiedas the ‘problem’, based on the results ofscanning demonstrating either large pre-ovulatory follicles or completed ovulation.Finally, lactational oestrus has emerged as

a ‘big problem’ globally, and is alsocharacterised by animals that do not comein heat after weaning at the expected timewithin seven days post weaning.When scanned, those animals will

however have corpora lutea, and it is thuslogical that they cannot cycle due toprogesterone-mediated inhibition of cyclicactivity. However, based on the ‘knowledge’ of the

presence of corpora lutea, strategichormonal protocols may then be developedspecifically for each farm to properly handlethis phenomenon (for instance by using theprostaglandin F2� analogue Clospresenol;Planate).Another good example for the value of

ultrasonography in pig production aresituations when changes to the reproductionmanagement are planned that maypotentially have an effect on the‘reproduction behaviour’ in the herdpopulation. n

Fig. 3A. Image obtained from an ovary of a non-gravid pig with a single ovarian cyst(white arrow) surrounded by several corpora lutea (two are marked with redarrows). This condition does not have consequences for fertility. Fig 3B. Polycysticovarian degeneration. There are only cysts (black ‘holes’), i.e. no ‘normal’ ovarianbodies such as corpora lutea in addition. This condition usually leads to life-longinfertility and is a reason for an immediate culling.

Fig. 4A. Image obtained from a non-gravid pig showing an example of uterine cross-sections (white arrows) with completely homogeneous echotexture (uniformly‘grey’). Fig. 4B. From a non-gravid pig showing an example of uterine cross-sections(white arrows) with heterogeneous echotexture (‘black’ areas or less ‘grey’ areaswithin the cross-sections). A heterogeneous echotexture always ‘belongs’ to folliclescapable of producing sufficient amounts of oestrogens (such as medium of large pre-ovulatory follicles). In cases where for example corpora lutea are present, a hetero-geneous echotexture is considered a sign of uterine disease.

3A 3B

4A 4B